An efficient way to look at a large set of coherent spectra (e.g. observed
in OTF mode) is to plot them as a 2-D image where the intensity is colour
coded. The image is formed by applying the LOAD on the current index.
Then the /INDEX option modify the single spectra plotting commands as
follow:

BOX /INDEX, which plots the frame, i.e. the entry number (Y axis) as
a function of the velocity and/or frequency (X axis). The ranges of X and
Y axes are controlled by the SET MODE command. SET MODE Y
always control the intensity range.

SPECTRUM /INDEX, which plots the image.

TITLE /INDEX, which writes a header above the frame. Range of
parameters (e.g. scan number, beta and lambda offsets, ...) are written.

PLOT /INDEX, which performs all of CLEAR; BOX /INDEX;
SPECTRUM /INDEX; TITLE /INDEX in a single operation.